Apple Cake with Quark Cream and Caramel

Preheat the oven to 170 °C (top/bottom heat). Line a springform pan (20-24 cm diameter) with baking paper.

Separate eggs. Beat 110 g butter with 140 g sugar, 20 g cinnamon sugar, and oil until creamy. Stir in the egg yolks one by one.

Mix flour, baking soda, baking powder, and 1 g salt. Alternately stir into the egg yolk mixture with the kefir. Fold in chopped nuts and 150 g grated apples.